High temperatures can effectively degrade residual tetracyclines in chicken manure through composting

Abstract

Tetracyclines (TCs) residues in livestock manure are the main origin of environmental tetracyclines contamination and have serious environmental and health risks. This work aimed to examine the effect of temperature on the degradation patterns of TCs antibiotics. Tetracycline (TC), doxycycline (DC), oxytetracycline (OTC) and chlortetracycline (CTC) were all degraded much more quickly in sterilized double distilled H₂O (ddH₂O) at higher temperatures and lost antibacterial activity after being incubated at 70 °C for 72 h. High pH value enhanced the degradation process of TCs solutions. Degradation products of the TCs were identified with LC/MS. The TCs from simulated composting with sterilized chicken manure and nonsterilized manure all showed temperature-dependent thermal degradation. The degradation pattern fitted the availability-adjusted loss model well. The fitted equations showed that the half-lifes of degradation of the TCs were 1.66-7.62 h at 70 °C, 3.29-21.39 h at 60 °C and 9.25-57.19 h at 50 °C. Compared with those of nonsterilized manures, we concluded that high temperature can effectively degrade the residual TCs in chicken manure by thermal degradation during high temperature composting. Temperatures that are elevated moderately, for example, up to 70 °C, during the composting process can make the degradation process more effective and rapid.

Keywords: Degradation; Simulated composting; Temperature; Tetracylines.